Emission/transmission device for use with a dual head nuclear medicine gamma camera with the transmission source located behind the emission collimator

Abstract

A SPECT system includes two radiation detector heads (32) and (34) which are mounted opposite each other to a gantry (30) for rotation about a subject. The subject is injected with a source of emission radiation, which emission radiation passes through a collimator (38) mounted on each detector head and is received by a radiation receiving face of the detector heads. A radiation source (40) is disposed between the collimator (38) of one detector head and the face of the one detector head. Transmission radiation from the radiation source (40) passes through the collimator (38), through the subject, and is received by the opposite detector head concurrently with the emission radiation. Alternately, a radiation source (40) is disposed behind the collimator of both detector heads (32, 34) such that both detector heads concurrently receive emission and transmission radiation. The detector heads (32, 34) generate emission and transmission projection data indicative of the received emission and transmission radiation. A sorter (70) sorts the emission and transmission projection data and the data is stored into a projection view memory (72). The emission data is corrected (78) in accordance with the transmission data and into a three-dimensional image representation (80).

Having thus described the preferred embodiment, the invention is now claimed to be: 
     
       1. A diagnostic imaging system comprising: a gantry for movably supporting first and second detector heads oppositely disposed on the gantry, each detector head receiving emission radiation from an examination region and generating emission data indicative thereof;   first and second collimators mounted on radiation receiving faces of the first and second detector head, respectively, for collimating the radiation received by the first and second detector heads;   a transmission radiation source mounted to traverse along the first collimator between the radiation receiving face of the first detector head and the examination region such that the second detector head receives both emission radiation from the examination region and transmission radiation from the transmission radiation source, the second detector head further generating transmission data indicative of the transmission radiation received;   a radiation blocking shield mounted to traverse along the first collimator with the transmission radiation source, the radiation blocking shield being disposed between the transmission radiation source and the first detector head radiation receiving face such that the transmission radiation is blocked from being received by the first detector head; and   a reconstruction processor for reconstructing a volumetric image representation from the emission and transmission data.   
     
     
       2. The diagnostic imaging system as set forth in claim 1 further including: a radiation source driver which moves the transmission radiation source longitudinally across the first collimator.   
     
     
       3. The diagnostic imaging system as set forth in claim 2 further including: a shielded area disposed at least at one side of the first collimator such that when the radiation source is positioned within the shielded area, transmission radiation is contained within the shielded area.   
     
     
       4. The diagnostic imaging system as set forth in claim 1 further including: a second transmission radiation source disposed between the second detector head and the collimator of the second detector head such that the first detector head receives both emission radiation from the examination region and transmission radiation from the second transmission radiation source, the first detector head generating transmission data indicative of the transmission radiation received from the second transmission radiation source.   
     
     
       5. The diagnostic imaging system as set forth in claim 1 further including: a sorter for sorting the emission and transmission data generated;   a memory for storing the emission and transmission data;   an emission data correction means for correcting the emission data in accordance with the transmission data and supplying the corrected emission data to the reconstruction processor.   
     
     
       6. The diagnostic imaging system as set forth in claim 1 wherein the first collimator defines a pair of guide members longitudinally along oppositely disposed side regions thereof, the radiation blocking shield and the transmission radiation source being mounted for translating movement along the guide members. 
     
     
       7. The diagnostic imaging system as set forth in claim 6 wherein the radiation blocking shield includes a generally U-shaped radiation blocking element which carries the transmission radiation source therein, the generally U-shaped element having an opening disposed toward the first collimator and being closed toward the first detector head, such that transmission radiation is emitted through the first collimator as the U-shaped element moves along the guide members. 
     
     
       8. The diagnostic imaging system as set forth in claim 7 further including at ends of the guide members, a radiation blocking shield which interacts with the opening of the U-shaped member to block the passage of transmission radiation. 
     
     
       9. The diagnostic imaging system as set forth in claim 1 wherein the radiation blocking shield, is disposed around the radiation source such that the transmission radiation is transmitted only in a direction towards the examination region. 
     
     
       10. The diagnostic imaging system as set forth in claim 1 wherein the transmission radiation source includes one of: a line source;   a bar source;   a point source;   a flat rectangular source;   a disk source; and,   a flood source.   
     
     
       11. A diagnostic imaging system comprising: a gantry for movably supporting first and second detector heads oppositely disposed on the gantry, each detector head receiving emission radiation from an examination region and generating emission data indicative thereof;   a first collimator grid mounted between the radiation receiving face of the first detector head and the examination region, for collimating the radiation received by the first detector head;   a second collimator grid mounted between the radiation receiving face of the second detector head and the examination region, for collimating the radiation received by the second detector head;   a movable transmission radiation source movably disposed between the first detector head and a front face of the first collimator grid, the second detector head receiving both emission radiation from the examination region and transmission radiation from the transmission radiation source, the second detector head further generating transmission data indicative of the transmission radiation received;   a radiation source shield surrounding a portion of the transmission radiation source such that transmission radiation from the transmission radiation source is directed toward the second detector head and blocked from being received by the first detector head; and   a reconstruction processor for reconstructing a volumetric image representation from the emission and transmission data.   
     
     
       12. In a diagnostic imaging system for examining a subject in an examination region who has been injected with a radiopharmaceutical having a first characteristic energy level, the imaging system including a pair of detector heads oppositely mounted across the examination region for receiving emission radiation emitted by the radiopharmaceutical and a reconstruction processor for reconstructing an image representation based on the radiation received by the detector heads, each detector head having a collimator mounted on a radiation receiving face of the detector heads, the improvement comprising: a transmission radiation source movably disposed between the collimator of one of the detector heads and its radiation receiving face, the transmission radiation source selectively transmitting transmission radiation having a second characteristic energy level through the collimators such that the other detector head concurrently receives both the emission radiation and the transmission radiation while the one detector head is shielded from receiving transmission radiation from the transmission radiation source.   
     
     
       13. A collimator for diagnostic imaging systems which include a detector head which has a radiation receiving face for receiving emission radiation from a subject which has been injected with a radiopharmaceutical, which radiation has passed through the collimator, the collimator comprising: a series of vanes, the vanes extending between a subject facing surface and a detector head facing surface;   a guide assembly disposed along the detector head facing surface of the vanes;   a carrier for carrying a transmission radiation source mounted to the guide assembly, the carrier being selectively translatable along the guide assembly behind the vanes such that the carrier temporarily blocks the emission radiation from reaching a portion of the radiation receiving face of the associated detector head during translation, the carrier blocking radiation from the carried transmission radiation source from impinging on the radiation receiving face of the associated detector head and directing the radiation from the carried radiation source through the vanes of the collimator toward the subject, whereby the radiation source carrier is selectively translatable along the guide assembly to transmit radiation toward the subject while the detector head radiation receiving face is receiving radiation emitted by the radiopharmaceutical injected into the subject.   
     
     
       14. A method of diagnostic imaging with a camera system including a first detector head having a first collimator mounted adjacent a radiation receiving face thereof and a second detector head having a second collimator mounted adjacent a radiation receiving face thereof, the first and second detector heads being disposed on opposite sides of an examination region and rotatable therearound, the method comprising: injecting a radiopharmaceutical into a subject in the examination region, the radiopharmaceutical emitting radiation of a first characteristic energy;   moving a radiation source along the first collimator between the first detector head radiation   receiving face and the examination region shielding a portion of the first detector head radiation face from receiving radiation emitted by the radiopharmaceutical, the radiation source being configured to transmit radiation toward the examination region;   shielding the radiation source to block radiation transmitted by the radiation source from being received by the first detector head;   moving the detector heads around the examination region;   with the first detector head, receiving radiation emitted by the radiopharmaceutical;   with the second detector head, receiving radiation transmitted from the radiation source and radiation emitted by the radiopharmaceutical through the second collimator.   
     
     
       15. The method of diagnostic imaging as set forth in claim 14 further including: separating output signals from the first and second detector heads which are attributable to emission radiation from output signals which are attributable to transmission radiation;   correcting the emission radiation output signals in accordance with the transmission radiation output signals;   reconstructing the corrected emission radiation output signals into an image representation.   
     
     
       16. The method of diagnostic imaging as set forth in claim 14 further including moving a second radiation source between the second detector head radiation receiving face and the second collimator such that the second radiation source transmits radiation through the second collimator toward the examination region and the first detector head. 
     
     
       17. The diagnostic imaging method as set forth in claim 14 further including: when the radiation source has been moved fully to one side of the radiation receiving face, shielding the radiation source to block radiation from being transmitted.